The invention relates to the field of a radio navigation, and, more specifically, to technical systems of personal safety, which allow the position-fix based on signals of a satellite radio navigational system xe2x80x9cGPSxe2x80x9d and message passing about position along with the messages of an emergency situation to a base monitoring station.
The systems of personal safety, considered here, are versions of systems of tracking of objects used in monitoring (tracking) or control. The development of this branchxe2x80x94the branch dealing with the observation of location of people, is justified by a prospect of development of receivers of GPS signals with such overall dimensions, weight and power consumption, that would allow construction of probable GPS receivers with personal means of mobile radio communication. Thus the task of minimization of overall dimensions, reduction of power consumption and simplification of receivers executing a position-fix on GPS signals, is one of most important.
The systems of tracking of objects, for example of vehicles (see application of Germany (DE) 3501035, Int. Cl. G08 G 1/00, publ. Jul. 17, 1986 [1], application EPO (EP) 0379198, Int. Cl. GO1 S 5/02, GO1 S 5/14, 30 publ. Jul. 25, 1990 [2], application EPO (EP) 0509775, Int. G01 S 5/14, publ. Apr. 15, 1992 [3]and patent of USA U.S. Pat. No. 5,319,374, Int. Cl. G01 S 1/24, G01 S 5/02, G01 S 3/02, G04 C 11/02, publ. Jun. 7, 1994 [4]), are known, in which the tracked objectxe2x80x94a vehiclexe2x80x94is supplied with the unit for a position-fix on GPS signals and equipment for radio communication with a central station, which carries out monitoring of the position of transport.
The systems are known, which track vehicles on GPS signals and, in case of an extreme situation, transmit the data about position to a tracking station (see, for example, application of Germany (DE) 3839959, Int. Cl. G08 B 25/00, G08 G 1/123, B60 Q 9/00, H04 Q 7/00, publ. Apr. 12, 1990 [5], patent of USA U.S. Pat. No. 5,355,140, Int. Cl. G01 S 1/08, G01 S 5/02, publ. Oct. 11, 1994 [6] and application PCT (WO) 93/16452, Int. Cl. G08 G 1/123, publ. Aug. 19, 1993 [7]).
In the considered systems of tracking and scheduling of vehicles [1-7] for a position-fix the standard receivers of GPS signals, equipped by additional units ensuring data transmission about site, and also alarm signals of a radio channel on station of tracking are used. As a rule, in such systems the receivers of GPS signals are not supposed to perform with strict requirements to minimization of the equipment and the power saving, and the tasks of a position-fix in conditions of partial blocking of a signal reception GPS are overcome, for example, by an integration with elements of inertial systems.
In contrast to systems for tracking transport, in systems of personal safety to receivers of GPS signals, operating for a position-fix, additional requirements can exist. On the one hand, it is justified by the necessity of accommodation of the receiver of GPS signals in a body of a radiophone (see, for example, Application EPO (EP) 0528090, Int. Cl. G01 S 5/00, publ. Feb. 24, 1993 [8]. This results in necessity to minimize means of receiving GPS signals and their power consumption. On the other hand, the requirements may be specified on provision of a position-fix in conditions of partial blockage of GPS signals, for example in operation conditions xe2x80x9cunder foliagexe2x80x9d, using thus only radio signals received from the air.
The receiver of GPS signals with communication channel for message passing about extreme situations (see application PCT (WO) 97/14057, Int. Cl. G01 S 5/14, G01 S 1/04, publ. Apr. 17, 1997) [9], is known in which the additional means ensuring a capability of a position-fix on GPS signals in conditions of their partial blockage are provided. The receiver described in [9], is selected as the prototype. The generalized skeleton diagram of the receiver adopted as the prototype, is shown on FIG. 1.
The receiverxe2x80x94prototype, see FIG. 1, contains an input unit 1 of conventional receiver of GPS signals, including sequentially connected radio frequency signal converter 2, whose input is also an input of the unit 1, and unit 3 for analog-to-digital conversions of signals, whose output is also an output of the unit 1, and also former 4 of signals of clock and heterodyne frequencies, whose control and reference inputs are control and reference inputs of the unit 1, respectively; whereby heterodyne input of the radio frequency signal converter 2 and clock input of the unit 3 are connected respectively to heterodyne and clock outputs of the former 4. The former 4 is supplied with means for formation of signal clock and heterodyne frequencies including, for example, synthesizers of frequencies, the pre-set inputs of which form a control input of the former 4. The synthesizers of frequencies work from the reference generator which is included in a structure of the former 4. In a case, where in the receiver the tuning of frequency of the reference generator by an external high-stable signal is provided, the reference generator is supplied with the appropriate tuning unit, for example unit PLLF, whose reference input forms a synchronization input (i.e., reference input) of former 4.
The receiverxe2x80x94prototype contains also output unit 5 of the conventional receiver of GPS signals, whose signal input is connected to an output of the unit 3 via the switch 6, and whose clock input is connected to a clock output of the former 4.
To the second output of the switch 6 are connected sequentially joint memory unit 7, for storage of calculated values of signals shaped by the unit 3, and signal processor 8. The clock input of the memory unit 7 is connected to a clock output of the former 4.
Control input of the former 4, control input of the switch 6, and also the data inputsxe2x80x94outputs of the signal processor 8 and unit 5 are connected by the appropriate data buses to the decision-making unit 9, whose structure includes a microprocessor for data processing, controller and memory unit for storage of programs and data.
The decision-making unit 9 is connected to the data input-output unit 10 and to the transceiver unit 11, executing reception and transmission of signals and data through the communication channel linking the receiver to a base station 12. In that case, when in the former 4 the tuning (synchronization) of the reference generator is performed using an external signal, the output of a reference signal (signal of synchronization) of transceiver unit 11 is supplied to the appropriate input of the former 4 (in FIG. 1, this connection is shown by a dotted line).
The data input-output unit 10 can be realized, for example, by an appropriate controller, keypad, and display supplied with an interface connector.
The transceiver unit 11 is realized as a modem and transceiver maintaining radio communication with a base station 12.
The base station 12 is supplied with means for a signal reception of an alarm and locating information of the receiver, and also with its own means for formation of the ephemeral data, rough coordinate information on position of the receiver, data of Doppler shift and means for transmission of these data through a radio channel to the unit 11. Besides, the base station 12 can be supplied with means for implementation of transmission of a reference signal for the said tuning of frequency of the reference generator of the receiver.
The receiverxe2x80x94prototype operates as follows. The GPS signals from an output of a receive antenna go to an input of the radio frequency converter 2 of the input unit 1, where the signal conditioning with downturn of frequency takes place. The mixers, which are included in a structure of the converter 2, working on heterodyne signals (Fr), coming from the appropriate outputs of the former 4, are used.
The former 4 synthesizes signals of clock (Ft) and heterodyne (Fr) frequencies, using for this purpose a signal of a reference frequency shaped by the reference generator included in a structure of the former 4. The pre-set of values of frequencies, shaped by synthesizers, is effected by applying to control inputs of synthesizers appropriate adjusting codes shaped by the unit 9.
From an output of the radio frequency converter 2 signals go to an input of the analog-to-digital conversions of a signal unit 3, where they will be converted to a digital kind. The sampling rate on time at analog-to-digital conversion is determined by a clock signal (Ft), coming from a clock output of the former 4. The output signals of the unit 3 form output signals of an put unit 1.
From an output of an input unit 1 signals go to an input of the switch 6, which operates under the influence of a control signal formed by unit 9.
In a usual mode, i.e. in the absence of blockage of GPS signals, the switch 6 executes connection of the unit 1 with the unit 5, which executes conventional correlation processing of received GPS signals, including searching for signals of frequency and delay, tracking of code, frequency and phase of carrier signals, extraction and decoding of a service information about ephemerises, extraction of the navigational information (determination of radio navigational parameterxe2x80x94RNP). In particular, thus the determination of a temporal position of peaks of correlation finctions of pseudo-noise signals of visible satellites used in the unit 5 in calculations of position. The correlation processing in the unit 5 is implemented with a clock rate determined by a clock signal (Ft), coming from a clock output of the former 4.
The locating information goes through the controller of the decision-making unit 9 to the unit 10 responsible for input-outputs of the data, where, for example, they are represented on the display.
The locating information goes also to the transceiver unit 11, which, in a communication session with a base station, transmits to a base station 12 locating information and, in case of an extreme situation, message on an extreme situationxe2x80x94alarm signal, which is shaped by means of the unit 10 and controller of the unit 11.
At a base station 12, independently of the functioning of the receiver, the formation of the ephemeral data, rough coordinate 180 information on position of the receiver and data of Doppler shift takes place, which through communication channel in communication sessions are transmitted to the transceiver unit 11. These data are used in operation of the receiver in adverse conditions of reception at a bad signal to noise ratio (i.e. in conditions of blockage of GPS signals).
In the said adverse conditions of reception (in conditions of blockage of GPS signals) the switch 6 connects an output of the unit 1 to an input of the memory unit 7, executing storage of calculated values of signals shaped by the unit 3.
The switching of the switch 6 will be performed by a signal shaped by the unit 9, for example, by results of unsuccessful searching for signals in the unit 5 or on a signal of the operator coming from the unit 10.
The unit 7 executes preliminary memorizing of all calculated values of signals shaped by the unit 3, on an interval of about 1 second, i.e., (2xc3x97106-4xc3x97106) calculated values. The stored calculated values of signals go to unit 7 with a clock rate determined by a clock signal (Ft), coming from a clock output of the former 4, i.e., with frequency (2-4) MHz.
Calculated values stored in memory unit 7 are used many times by the signal processor 8, which executes, by purely software means, correlation processing of received GPS signals and determines a temporal position of a maximum of a correlation function for a signal of each satellite, i.e., its pseudo-range. The measured pseudo-ranges go to the processor of the unit 9, where the position-fix takes place. Thus, for implementation of correlation processing and the position-fix in said adverse conditions of reception, the ephemerical data, rough information on position (to within xc2x1150 km) and Doppler shifts of carrier frequencies of satellites obtained by the unit 9 on communication channel from a base station 12 are used. Besides, with the help of a clock signal transmitted by a base station 12, the frequency of the reference generator of the former 4 (described above) is tuned, or the frequency drift of the reference generator from a nominal value is measured.
The locating information determined in the unit 9, go to the unit 10 for indication, and also to the unit 11 for transmission to the base station 12, which tracks the receiver. Together with a locating information transmitted to a base station, if necessary, the messages on extreme situationsxe2x80x94alarm signals xe2x80x94are transmitted, which are shaped by means of the unit 10 and are transmitted through a communication channel to a base station 12 with the help of the unit 11.
Thus, receiver-prototype provides a capability of position-fix and transmission of alarm signal together with a locating information both in a normal conditions of GPS signal reception, and in conditions of signal blockage, that determines the receiverxe2x80x94prototype""s capability of use in systems of personal safety.
The realization of said functions in the receiverxe2x80x94prototype was implemented at the expense of its essential complication in comparison with conventional receivers of GPS signals. That is, in addition to usual units 1 and 5, used in conventional GPS receivers, in the receiverxe2x80x94prototype the decision-making unit 9 and signal processor 8, implemented on the basis of a fast-response microcomputer, and also the memory unit 7, implemented on the basis of a fast-response RAM of a high capacity for storage of calculated values, which, as a rule, is characterized by high power consumption and cost. All these contribute to big overall dimensions, weight, power consumption and cost of the receiver.
The problem which is solved by the present invention, is the creation of a receiver of GPS signals for a system of personal safety, which, in contrast to conventional receivers and to the receiverxe2x80x94prototype described above, is easy to realize, has lower power consumption, smaller overall dimensions and weight, smaller cost, and at the same time, retains all functions of the receiverxe2x80x94prototype and achieves about the same characteristics on a position-fix in an adverse conditions of GPS signal reception.
According to an embodiment of the present invention, the receiver of GPS signals for a system of personal safety contains sequentially joint input and output units, data input-output unit and transceiver unit intended for reception and transmission of signals and data on a communication channel linking the receiver to a base station. The reference signal output of the transceiver unit is connected to a reference input of an input unit. The clock input of the output unit is connected to a clock output of an input unit. The input unit contains sequentially joint radio frequency converter, whose signal input is a signal input of an input unit, and unit of analog-to-digital signal converter, whose output is a signal output of an input unit, and also a former of signals of clock and heterodyne frequencies, whose reference input is a reference input of an input unit. The heterodyne output of the generator of signals of clock and heterodyne frequencies is connected to a heterodyne input of the radio frequency converter of signals, and the clock output, which is a clock output of an input unit, is connected to a clock input of the unit of analog-to-digital conversion of signals. The output unit of the receiver of GPS signals is a unit containing multichannel digital correlator, where N=8-12 channels of parallel processing, linked with a microprocessor equipped with permanent storage, for storing signal processing programs and operative storage, for data storage when operating in a standard mode without blockage of GPS signals. The microprocessor of the output unit is connected by data buses to the generator of signals of clock and heterodyne frequencies of the input unit, to the data input-output unit, to the transceiver unit and to an additional unit for permanent storage of signal processing programs and operative storage of data and calculation values of the multichannel digital correlator operating in conditions of blockage of GPS signals. Each of the N channels of the multichannel digital correlator is equipped with K inphase and K quadrature correlators, where K=20-40, connected with the appropriate storage units ensuring the capability of simultaneous correlation of GPS signals with K copies of C/A code, shifted by one half of a digit of C/A code of a GPS, and coherent accumulation of the results of correlation on an interval equal to duration of epoch of C/A code.
In a preferred embodiment of the present invention, the receiver is designed in such a way that each of the channels of the multichannel digital correlator comprises: a digital controlled generator of a carrier frequency; a control register; a digital controlled code generator; a generator of reference C/A code of GPS; a programmed delay line; first and second digital mixers of inphase and quadrature processing channels, respectively; first and second groups of K inphase and quadrature correlators, whose first inputs are connected to out-puts of the appropriate digital mixers, second inputs are connected to the appropriate outputs of a programmed delay line, and outputs are connected to signal inputs of the appropriate storage units; and a data exchange unit linking the outputs of storage units, control input of the digital controlled generator of carrying frequency, control input of the register of control input of the digital controlled generator of a code and first input of the generator of reference C/A code with the microprocessor of the output unit. The signal inputs, linked with each other, of digital mixers form a signal input of the channel. Linked with each other, the clock inputs of the controlled digital generator of the carrier frequency, of the digital controlled generator of a code of a programmed delay line and of the storage units, form a clock input of a channel. The second inputs of the first and second digital mixers are connected respectively to the first and second outputs of the digital controlled generator of the carrier frequency. The signal and control inputs of a programmed delay line are connected respectively to an output of the generator of reference C/A code of the GPS and to the first output of the control register. The second out-put of the control register is connected to the second input of the generator of reference C/A code of the GPS. The third input of the generator of reference C/A code of the GPS is connected to an output of the digital controlled generator of the code. In the multichannel digital correlator, the signal inputs of channels, linked with each other, and the clock inputs of channels, also linked with each other, form, respectively, the signal and clock inputs of the multichannel digital correlator.